Build with the system NSPR library instead of the bundled version.

Originally based on this Debian patch:
https://salsa.debian.org/chromium-team/chromium/-/blob/master/debian/patches/system/nspr.patch

diff --git a/base/BUILD.gn b/base/BUILD.gn
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -184,6 +184,12 @@ buildflag_header("ios_cronet_buildflags") {
   flags = [ "CRONET_BUILD=$is_cronet_build" ]
 }
 
+if (is_linux) {
+  ldflags = [
+    "-lnspr4",
+  ]
+}
+
 # Base and everything it depends on should be a static library rather than
 # a source set. Base is more of a "library" in the classic sense in that many
 # small parts of it are used in many different contexts. This combined with a
@@ -838,8 +844,6 @@ mixed_component("base") {
     "third_party/cityhash_v103/src/city_v103.cc",
     "third_party/cityhash_v103/src/city_v103.h",
     "third_party/icu/icu_utf.h",
-    "third_party/nspr/prtime.cc",
-    "third_party/nspr/prtime.h",
     "third_party/superfasthash/superfasthash.c",
     "thread_annotations.h",
     "threading/hang_watcher.cc",
diff --git a/base/time/pr_time_unittest.cc b/base/time/pr_time_unittest.cc
--- a/base/time/pr_time_unittest.cc
+++ b/base/time/pr_time_unittest.cc
@@ -6,7 +6,7 @@
 #include <time.h>
 
 #include "base/compiler_specific.h"
-#include "base/third_party/nspr/prtime.h"
+#include <nspr/prtime.h>
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "testing/gtest/include/gtest/gtest.h"
diff --git a/base/time/time.cc b/base/time/time.cc
--- a/base/time/time.cc
+++ b/base/time/time.cc
@@ -21,7 +21,7 @@
 #include <utility>
 
 #include "base/strings/stringprintf.h"
-#include "base/third_party/nspr/prtime.h"
+#include <nspr/prtime.h>
 #include "base/time/time_override.h"
 #include "build/build_config.h"
 #include "third_party/abseil-cpp/absl/types/optional.h"
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</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=05044a54468e091ead1dfa24662df02cd0929ad8'>root</a>/<a href='/guix/log/doc?id=05044a54468e091ead1dfa24662df02cd0929ad8'>doc</a>/<a href='/guix/log/doc/fdl-1.3.texi?id=05044a54468e091ead1dfa24662df02cd0929ad8'>fdl-1.3.texi</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/doc/fdl-1.3.texi?id=05044a54468e091ead1dfa24662df02cd0929ad8&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-03-10 20:26:52 +0100'>2020-03-10</span></td><td><a href='/guix/commit/doc/fdl-1.3.texi?id=21656ffa3b6d78a610f0befced20cc9b4b3baab6'>doc: Use HTTPS for external links.</a><span class='msg-avail'>...<span class='msg-tooltip'>* doc/contributing.texi
  (14.1 Building from Git,
   14.3 The Perfect Setup,
   14.4.1 Software Freedom,
   14.4.4 Synopses and Descriptions,
   14.5.4 Formatting Code):
   Use HTTPS for @uref{}s and @url{}s that support it.

* doc/fdl-1.3.texi
  (Appendix A GNU Free Documentation License):
  Use HTTPS for @uref{}s and @url{}s that support it.

* doc/guix.texi
  (6.3 Build Systems,
   8.8.4 Networking Services,
   8.8.8 Sound Services,
   8.8.16 Web Services,
   8.11 Name Service Switch,
   12.2 Preparing to Use the Bootstrap Binaries);
   Use HTTPS for @uref{}s and @url{}s that support it.

Signed-off-by: Marius Bakke &lt;mbakke@fastmail.com&gt;
</span></span></td><td>Vitaliy Shatrov</td></tr>